An old estimate of the frequency of lightning on Earth was 100 times a second. In 1997 NASA and National Space Development Agency (NASDA) of Japan launched the first Lightning Imaging Sensor (LIS) equipped satellite that can detect and record lightning, including in places where there is nobody to observe it.[1]

Lightning is now known to occur on average 44 (± 5) times a second averaged over the entire earth, for a total of nearly 1.4 billion flashes per year.[2][3]

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The lightning flash rate averaged over the earth for intra-cloud (IC) + cloud-to-cloud (CC) to cloud-to-ground (CG) is at the ratio: (IC+CC):CG = 75:25. The base of the negative region in a cloud is normally at roughly the elevation where freezing occurs. The closer this region is to the ground, the more likely cloud-to-ground strikes are. In the tropics where the freeze zone is higher the (IC+CC):CG ratio is about 90:10. At the latitude of Norway (60° lat.) where the freezing elevation is lower the (IC+CC):CG ratio is about 50:50.[4][5]

Global map of lightning frequency--strikes/km2/yr. The high lightning areas are on land located in the tropics. Areas with almost no lightning are the arctic and antarctic closely followed by the oceans with only 0.1 to 1 strikes/km2/yr there.

Different locations have different numbers of storms and lightning strikes. In the United States, for example, Florida experiences the largest number of recorded strikes in a given period during the summer season. As much of Florida lies on a peninsula, it is bordered by the ocean on three sides. The result is the nearly daily development of clouds that produce thunderstorms. The west coast of the United States has the fewest lightning strikes.[6]

The map on the right show that lightning is not distributed evenly around the planet.[7] Approximately 70% of lightning occurs on land located in the tropics where the majority of thunderstorms occur. The north and south poles and the areas over the oceans have the fewest lightning strikes. The place where lightning occurs most often (according to the data from 2004 to 2005) is near the small village of Kifuka in the mountains of eastern Democratic Republic of the Congo,[8] where the elevation is around 975 metres (3,200 ft). On average this region receives 158 lightning strikes per 1 square kilometer (0.39 sq mi) a year.[3]

Above the Catatumbo river, which feeds Lake Maracaibo in Venezuela, Catatumbo lightning flashes several times per minute, 140 to 160 nights per year, accounting for about 25% of the world's production of upper-atmospheric ozone. Singapore has one of the highest rates of lightning activity in the world.[9] The city of Teresina in northern Brazil has the third-highest rate of occurrences of lightning strikes in the world. The surrounding region is referred to as the Chapada do Corisco ("Flash Lightning Flatlands").[10]

In the US, Central Florida sees more lightning than any other area. For example, in what is called "Lightning Alley", an area from Tampa, to Orlando, there are as many as 50 strikes per 1 square mile (2.6 km2) (about 20 per 1 km2 or 0.39 sq mi) per year.[11][12] The Empire State Building is struck by lightning on average 23 times each year, and was once struck 8 times in 24 minutes.[13]

World map showing frequency of lightning strikes, in flashes per square kilometer (km²) per year (equal-area projection). Lightning strikes most frequently in the Democratic Republic of the Congo.Combined 1995–2003 data from the Optical Transient Detector and 1998–2003 data from the Lightning Imaging Sensor.

Official maps have delays in minutes (Canada,[14] USA[15]) or even hours (Europe[16]), whereas the amateur network Blitzortung has delays usually under ten seconds.[17]